In the related art, fluorescence endoscopes with which fluorescence coming from a living organism is observed by radiating excitation light thereon have been employed for the purpose of early detection of cancer or the like (for example, see Patent Literature 1). The fluorescence endoscopes include: binocular types provided with a white-light-observation-dedicated image-acquisition device and a fluorescence-observation-dedicated image-acquisition device; and monocular types provided with a single image-acquisition device that serves for performing both white-light observation and fluorescence observation. An endoscope light source apparatus described in Patent Literature 1 realizes illumination modes that are suitable for a binocular-type fluorescence endoscope and a monocular-type fluorescence endoscope, respectively, by using a single lamp light source and by changing combinations of a plurality of filters to be disposed on an optical path.